Background: While baseline blood pressure (BP) is a known predictor of 90-day residual deficit after acute ischemic stroke, the effect of thrombolysis on this relationship has not been described. To study the interaction and to find intervals of prognostic significance, the functional forms of this predictive relationship should be found and compared for recombinant tissue plasminogen activator (rt-PA)- and placebo-treated patients of the first European Cooperative Acute Stroke Study.
Methods: We studied the 615 patients with acute ischemic hemispheric stroke randomized and treated in the first European Cooperative Acute Stroke Study. Endpoints were fatal outcome within and favorable outcome (no or negligible long-term handicap on the modified Rankin Scale scores 0 or 1) after 90 +/- 14 days. Functional relationships with baseline BP were estimated fully nonparametrically as moving averages of occurrences of either outcome among placebo- and rt-PA-treated patients, separately. Visual findings were corroborated by conventionally stratified logistic regression.
Results: For favorable outcome, an S-shaped functional relationship with baseline systolic BP (SBP) was found with an averaged incremental rate around 10% per 1 mm Hg increase in baseline SBP between 140 and 160 mm Hg, among rt-PA and placebo patients. Similar results were obtained for diastolic BP (DBP) between 80 and 90 mm Hg. Odds ratios in favor of rt-PA were 1.96 (95% CI: 1.02-3.78) and 2.87 (95% CI: 1.36-6.04) for SBP and DBP in these intervals, respectively. For mortality, visible markedly lower risks in the placebo group between 120 and 140 and between 160 and 180 mm Hg SBP were confirmed with adjusted OR of 2.47 (95% CI: 1.09-5.64) and 9.73 (95% CI: 2.02-46.82), respectively.
Conclusions: Patients benefited from rt-PA in terms of no or negligible handicap after 90 days, without excess risk of death, with baseline SBP between 140 and 160 mm Hg or baseline DBP between 80 and 90 mm Hg.